1. Field of the Invention
The present invention relates to a driving device, a light-emitting device and a projector.
2. Description of Related Art
For example, a switching regulator (switching power source or DC-DC converter), serving as a power source, is a circuit that converts a DC input voltage to a DC output voltage through a turning on/off operation of a switching element and is used as a power source or driver having various loads. The output current or voltage from the switching regulator is controlled by a feedback control system so as to be maintained at a constant target value.
Electric power can be supplied in sequence from a single switching regulator to a plurality of loads through sequential selection of the loads with a selector installed at the output of the switching regulator (for example, refer to FIG. 25 in Japanese Patent Application Laid-Open No. 2004-311635).
If different currents are supplied to individual loads, the output current of a switching regulator having a variable target value is switched for each load in synchronization with the selection of the load.
When a light-out period, during which no load is selected, is provided between a load-selected period and the next load-selected period, the circuit for the output of the switching regulator (i.e., a power source) is opened. Accordingly, during the light-out period, energy accumulated in a circuit element, such as an inductor, inside the switching regulator is not absorbed, leading to an increase in the output voltage from the switching regulator. Such a phenomenon results in a delay in the response of the output voltage and/or the output current from the switching regulator in the subsequent load-selected period. This extends the period of time required for the output voltage and/or the output current to reach a target value.